It is estimated that 178,700 American women will be diagnosed with breast cancer in 1998. A large proportion of these women will receive adjuvant chemotherapy, radiotherapy, and/or hormonal therapy based on evidence indicating that such treatment extends disease-free survival as well as overall survival. As more women receive adjuvant treatment, there is growing recognition of the potential for long-term side effects. Along these lines, it has been shown that administration of adjuvant chemotherapy can result in secondary leukemia, cardiotoxicity, and ovarian failure. Clinical observations and a limited number of research reports suggest that persistent fatigue may also be a long-term side effect of adjuvant chemotherapy. Although fatigue has been identified as one of the most frequent and distressing symptoms affecting breast cancer patients treated with adjuvant chemotherapy, relatively little is known about its characteristics, etiology, or treatment. We propose to address these issues by conducting the first controlled, longitudinal study of fatigue in breast cancer patients before, during, and after adjuvant chemotherapy and radiotherapy treatment. Women with early stage breast cancer scheduled to receive adjuvant treatment will be recruited and undergo a baseline assessment before the start of chemotherapy. Additional assessments will be performed during the course of chemotherapy and before and during a subsequent course of radiotherapy. Following completion of radiotherapy, patients will continue to be monitored for six months. An age-matched sample of women with no history of cancer will be recruited and monitored over a six-month period for comparison purposes. These data will be used: 1) to determine the severity, chronicity, and course of fatigue associated with adjuvant treatment of breast cancer; 2) to characterize the cognitive, affective, and behavioral manifestations of fatigue that persists following completion of adjuvant treatment; and 3) to test the utility of a cognitive-behavioral model designed to explain the perpetuation of fatigue following completion of adjuvant treatment. Preliminary analyses of study data are expected to provide empirical support for adaptation and pilot testing, during the final months of funding, of a cognitive-behavioral intervention originally developed for chronic fatigue syndrome for use with breast cancer patients experiencing persistent fatigue related to adjuvant treatment.